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Neurology Research Center Kerman University of medical sciences

Early neurologic complications and death rate after coronary artery bypass graft

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Med ID: 195
Read Online: 479
Published Online: 20 , January, 2020
Condition: Accepted
In Subjects: Neurology

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Hossein Ali Ebrahimi, Narges Khanjani, Mahmood Khodarahmi


Abstract

Introduction: Coronary artery bypass graft surgery (CABG) is among the most frequent surgical procedures performed on the heart. Perioperative mortality and neurologic complications are common, sequence 1.6%, and 1.9%.We performed a retrospective study on patients who underwent CABG at the Shafa Medical center in Kerman University of Medical sciences from Kerman city of Iran, and compared it with a study done about 15 years age in this center, and also match it with other reports.

Methods: This cohort study, 1992 isolated CABG operations that had been carried out between 2010 and 2012 in Shafa Medical Center of Kerman University of medical sciences were reviewed. Postoperative neurologic complications in-Hospital were defined as follows: permanent central neurologic deficit, unresponsive coma for > 24 h, seizure and death.

Result: at first analysis, 31 (1.6%) have been died. The rate of death is more in female than male. Severe neurologic complications in the Hospital postoperative period were 2.8%. The most common were encephalopathy and strokes. The neurologic complications and mortality rate are higher in female and old age. Longer duration of pump usage is associated with higher mortality and neurologic complications. The mortality rate and neurologic complications were not associated with hypertension, diabetes, and hyperlipidemia.

Conclusion: We observed an improvement in Coronary Artery Bypass Graft with significant decrease in mortality rate and neurologic complications

Keywords: CABG, neurologic complications, mortality, Coronary artery bypass graft.

Introduction

Coronary artery bypass graft surgery (CABG) is among the most frequent surgical procedures performed on the heart. In Kerman city with more than 500000 populations 135 CABG performed at 1997(1), but this rate at know is increased. Although CABG has a beneficial effect on the heart, this procedure has adverse events on the central nervous system (CNS) (2,3,4,5,6). Stroke, early and late cognitive decline, seizure, and neuropathy have been reported previously following CABG 2,4,7. Complications can involve any part of the central and peripheral nervous systems. "Neurologic complications are always a risk with cardiac surgery, especially in older patients who have other health problems. Strokes are the most common neurologic complication after cardiac surgery in adults. In children, seizures are the most common neurologic complication (8). The involved cerebrovascular territories in different geographic areas are varied, In Kerman city intracranial artery involvement was the most prevalent finding in patients with thrombotic stroke in Kerman. Also posterior cerebral artery stenosis was more prevalent than anterior artery stenosis (9).

CNS disorders after coronary artery bypass grafting (CABG) significantly increase perioperative mortality and hospitalization time, and can lead to a decrease in the patient’s quality of life. The reported rate of major postoperative neurologic complications, such as stroke, varies from 0.8 to 6%10.11,12, 13. Neurologic complications are second only to heart surgery failure as a cause of morbidity and mortality following cardiac surgery significantly increases the likelihood of requiring long-term care (8,14).

Among the 1,395 patients enrolled in a final analysis, 27 (1.9%) had severe neurologic complications in the two weeks postoperative period. (15,16) From the University of Ottawa Heart Institute in Ontario, Canada, a 25 year study of 1,388 patients who underwent bypass surgery at an average age of only 48 years reveals an annual mortality of 2% (17).

Risk factors for neurological complications following CABG have also been described, In multivariate analysis, female sex, prior CABG surgery, ejection fraction <40%, urgent or emergency surgery, advanced age (70–79 year and >80 year), peripheral vascular disease, diabetes, dialysis-dependent renal failure and three-vessel coronary disease were significant predictors of fatal postoperative heart failure. 5,18,11,14.

Neurologic complications of CABG are strongly associated with increased morbidity and mortality. Identifying preoperative risk factors for neurologic injury may enable us to refine our perioperative approach, and to lessen or avoid these complications. Neurologic complications are second only to heart failure as a cause of morbidity and mortality following cardiac surgery, and the presence of neurologic sequel significantly increases the likelihood of requiring long-term care (19, 20).

We performed a retrospective study on patients who underwent CABG at the Shafa Medical center in Kerman University of Medical Sciences from Kerman city of Iran, and compared with a study was done about 15 years age in this center, and also match with other reports.

Methods

Patients: In this cohort study, 1992 isolated CABG operations (all of operations) followed to delivery of bed, that had been carried out between 2010 – 2012 the Shafa Medical Center of Kerman University of medical sciences were reviewed. Patients with incomplete intraoperative or postoperative data were excluded from study.

Intraoperative Patient Management: The conduct of anesthesia and CPB was standardized by hospital practice. Anesthesia was induced with midazolam (0.06 to 0.08 mg/kg), sufentanil (1 to 1.5 μg/kg), and pavulon (0.1 mg/kg), and was maintained with sufentanyl (0.5 to 1.25 μg/kg/h) and/or propofol infusion (3 to 6 mg/kg/h). The bypass circuit consisted of a hollow fiber oxygenato, an arterial line filter, and a roller pump. The circuit was primed with a mixture of colloidal intravenous infusion solution [3.5%; 1,200 to 1,300 mL], mannitol (20% solution; 200 mL), human albumin (20%; 100 mL), NaHCO3 (8.4%; 50 mL), potassium chloride (20 mmol), and heparin (50 mg/1,000 mL colloidal intravenous infusion solution). CPB was carried out by means of pulsatile flow with a flow range of approximately 2.4 L/min/m2. Moderate hypothermia (ie, temperature, 28°C to 32°C) was applied during the CPB. A modified St. Thomas solution was used to arrest the heart and to maintain it in an isoelectric state. After the release of the aortic clamp, a nitroglycerine infusion (0.5 μg/kg/min) was started. In the patients which need to coronary endartrectomy, have done. We didn’t used any drug that effect on cognition.

Data Collection : All demographic and clinical data were stored in using a software program. Postoperative neurologic complications were defined as follows: permanent or transient central neurologic deficit, unresponsive coma for > 24 h, seizure and death. In all cases, patients with possible neurologic complications were investigated by a neurologist. The variables; age, sex, diabetes mellitus, hypertension, hyperlipidemia are detected. Results were analyzed with independent t-test.

Results

Among 1992 patients enrolled at the first analysis, 31 (1.6%) have been died. Mortality rate was more in female than male (p=0.002). Table 1 showed concomitant disorders with CABG.Mortality rate in diabetic patients were lower, but non-significant (p=0.3). The rate of death in hypertensive patients were more, but non-significant (p=0.26). The rate of death in patients with hyperlipidemia were lower, but non-significant (p=0.25). Table 2 showed relation mortality with some disorders. The mean age is higher among death subjects (patients is 58.84±10.05, but in death cases was 61.49±8.71). The rate of death in older patients was more (p=0.000). The rate of death was higher in patients that have longer duration of pump usage (p=0.002). The rate of death was not associated with the number of grafts (p=0.75). 20 (2.8%) cases had severe neurologic complications in the Hospital postoperative period. Twenty percent of these patients suffered from cerebrovascular insults and 80% suffered from encephalopathy. No patients in this group developed seizures or peripheral nerve lesions.

Table 1: Concomitant disorders and CABG

Disorder
Number
Percent
Diabetes 81 11.3%
Hypertension 155 21.6%
Lipid disorder 109 15.2%
Diabete+Hypertnsion 40 5.6%
Diabete+Lipid disorder 49 6.8%
Hypertension+Lipid disorder 70 9.7%
Hypertension+Lipid disorder+diabetes 42 5.8%
Total
162/708
100%

Table 2: The rate of death and concomitant disorder

Death/Malady
Hypertension
Diabetes
Lipid disorder
No 15/406=3.7% 24/493=4.8% 22/430=5.1%
Yes 16/302=5.2% 7/215=3.2% 9/278=3.2%
P Value 0.261 0.296 0.251

Discussion

In this study 1992 patients from 2010-012 enrolled, in-hospital death rate was 1.6%. This finding is the same as other reports. This study compared to 6.6% in 1997 from this center, showed a significant decreased mortality rate (1). In 2009, in-hospital mortality rates for patients who underwent bypass surgery was about 1.54 percent, the report said, compared to 3.23 percent in 1994 (21). We think this decrease death rate is due to development in surgery technics.

The neurologic complications rate was 2.8%, these events were stroke (20%) and encephalopathy (80%), but seizure and peripheral nerve lesion were not detected. This rate compared to 3.7% (stroke 40%, encephalopathy 60%) in 1997 in this center, has a decrease rate.(1) In a study of 591 patients from nine medical centers in North America, the in-hospital complication rate was 1.5%. (22) Of the 587 coronary artery bypass surgeries performed at over a two year period, 2.04% of these patients developed neurologic complication in the two weeks following the surgery.(23) in another study the rate of neurologic complication (stroke) was reported 2.6% (24). The incidence of perioperative neurological problems in other study was 1.7 % in the CABG group (24).Among the 1,395 patients enrolled in an analysis, 27 (1.9%) had severe neurologic complications in the postoperative period. A direct comparison of both patient groups points with or without neurologic complication; the patients with postoperative neurologic complications were older (15).

The incidence of stroke related to cardiac operations ranges from 0.4 percent to 6 percent in different series, depending upon patient populations and specific procedures (19,20, 26, 27). In our study the stroke rate was 0.58%.

Intraoperative strokes occur in cardiac surgical patients by two major mechanisms. 1-Cerebral hypoperfusion can result from intraoperative hypotension and/or diminished cardiac output. 2- Arterial emboli can cause transient or permanent occlusion of cerebral vessels and produce cerebral ischemia. Arterial emboli can arise from multiple sources during cardiac operations: air emboli enter the arterial circulation via open cardiac chambers, vascular cannulation sites, or arterial anastomoses, while debris can be released during clamping and unclamping of the ascending aorta (28,29), constructing the proximal coronary artery bypass graft anastomoses in the ascending aorta, excising severely calcified and diseased cardiac valves, or by turbulent high-velocity blood flow from the aortic cannula within a diseased aorta.

Untreated hyperlipidemic patients have been shown to have a higher risk of post-CABG events than that of treated hyperlipidemic patients and those with normal serum lipid concentrations (30). In this study the rate of death in patients with hyperlipidemia are lower, but non-significant (p=0.25). All hyperlipidemic patients treated by anti-hyperlipidemic agents.

Patients with diabetes are at increased risk for coronary artery disease and frequently require coronary artery bypass grafting (CABG). In fact, 16% of all patients undergoing CABG in Canada have diabetes (31). Our finding about the rate of death in diabetic patients is lower, but non-significant. The in-hospital mortality rate for Canadian diabetic patients undergoing CABG is ∼4%, the rate of death in-hospital 8 (3%) died, 7 (2%) suffered nonfatal stroke (32).

Well established that hypertension is the main risk factor for stroke (33). The concomitant occurrence of atherosclerotic plaques in carotid, coronary and peripheral vessels has been described in a number of studies (34). Hypertension affects approximately 25% of the adult population in the United States, or 50 million people (35, 36). In a study, approximately 30% (612 of 2069) of the patients who had CABG surgery also had isolated systolic hypertension (37). In this study the rate of hypertension in patients who had CABG was 42% (284 of 665). Hypertension increases the risk of perioperative cardiovascular morbidity in patients who have CABG surgery, especially systolic hypertension (38, 39).

Although all nerve injuries are not preventable but proper attention to patient positioning and padding of potential pressure points can reduce the risk of injury. In other studies the peripheral nerve injury is reported unusual too (40). Upper extremity peripheral nerve injury follows cardiac operations in 2 to 15 percent of patients (41, 42, 43). Putative mechanisms of injury include brachial plexus traction, brachial plexus compression between the clavicle and the first rib during sternal retraction and nerve injury during internal mammary artery dissection. In this study didn’t find any important peripheral nerve injury, but we can’t roll out minor or transient nerve injury.

Conclusion: We observed an improvement in Coronary Artery Bypass Graft with significant decrease in mortality rate and neurologic complications. The most common neurologic complications were encephalopathy and strokes. The neurologic complications and mortality rate were higher in female and old age. Longer duration of pump usage was associated with higher mortality and neurologic complications. Factors such as diabetes, hypertension and hyperlipidemia were not associated with perioperative CABG neurologic complications and mortality.

Acknowledgement: This article is emerged from a research project from neurology research center-Kerman University of Medical Sciences-Kerman-Iran. Special thanks to Zahra Farrokhdost for her data collection.

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